1. Field of the Invention
The present invention relates generally to devices and methods for depositing layers of material upon substrates, and more particularly to electric arc vacuum deposition devices and methods.
2. Description of the Prior Art
Devices and methods to perform electric arc vapor deposition are known in the prior art, however there are problems with prior art devices which the present invention overcomes.
In U.S. Pat. No. 4,511,593, entitled Vapor Deposition Apparatus and Method, by Henry E. Brandolf, the substrate temperature during the deposition process increases due to direct heat and energized particle radiation from the source or from re-radiation of heat from a line of sight deposition shield. The heat radiated on the substrates causes the substrate temperature to rise, and this high temperature limits the application of this prior art device to only substrates that do not melt or outgas at those prevalent deposition temperatures. Also, in many situations, the deposition films may break away from the substrates due to film layer stress when the substrate temperature is decreased after the deposition process.
In other prior art devices, the sources may require significant cooling. U.S. Pat. No. 4,622,452, entitled Electric Arc Vapor Deposition Electrode Apparatus, by Bergman, et al., improves this source cooling problem somewhat by making the source itself form a wall of the cooling chamber and mounting the source to the cathode assembly by a central stud. A drawback of the Bergman invention is that if the source is not securely and uniformly tightened to cathode body to form a water tight engagement with a peripheral seal, water or water vapor will leak into the vacuum chamber, and any water leakage into the chamber is detrimental to the chamber vacuum and the deposition process. Also, with some prior devices, the film that is deposited on the substrate is generally sparse and characterized by columnar crystal growth that is separated by voids. This means that the film is not a good barrier against the diffusion of solids, liquids and gases through the film.